SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2321ae23b0fc793f367afa21811645faa51611fe28b47ebb92ea8528e5289b5d' 
  AND token = 'za/JThlAqBY8FY4F5JnLqgGPmuikmWkvkHOtdZ67Ln8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}